Joss Whedon is just a hairbreadth away from finishing Avengers: Age of Ultron, and he looks like he’s been shot out of a cannon.

His clothes are rumpled and baggy. So is the skin around his eyes. He started shooting the movie a year ago—jetting around the world from South Africa to Italy to the United Kingdom to South Korea—before arriving at Shepperton Studios outside London last May. There, the director was a high-powered burst of energy, pinballing around the set and voicing the off-camera part of the villain Ultron when James Spader wasn’t around.

But on this afternoon a few weeks ago, in late March, he shuffles into a black-box editing suite on the Walt Disney Studios lot in Burbank and slips into the corner of a couch looking like a pair of discarded pajamas. “Two days from now, I will finish this,” he says, like someone who thinks it may finish him first. “I moved next door [to temporary quarters on the studio lot], said goodbye to my kids…. I wake up, come here, and then I do this, and then I go to sleep. That’s it.”

Age of Ultron pits Iron Man, the Hulk, Thor, Captain America, Black Widow, and Hawkeye against Ultron, a genocidal artificial intelligence designed to protect the world, and Whedon says this is the end of the line for him. He’s wrapping up a three-year deal with Marvel Studios that included laying the foundation of this interlocked universe with 2012’s The Avengers, creating the ABC series Agents of S.H.I.E.L.D., and consulting on all manner of Marvel movies, from features to shorts. In other words, he’s about to be shot out of a canon, too. No wonder he’s beat.

But there’s no need to shed tears for him just yet. “Joss will be okay,” a crew member says in the elevator later, when I express my concern. “He’s about to make $2 billion.”

That’s probably a little low. Age of Ultron is likely to outgross the previous Avengers’ $1.56 billion global haul, and while Whedon won’t personally be pocketing all that cash, it’s fair to say that the stakes, and fan expectations, are high. “The first rule of making a sequel is: Take the best moments and do something else,” he says. “Don’t do the Indiana Jones gun trick again differently. Just go somewhere else.”

So where else did he go this time?

Love. Control. Creation. What we have with Avengers: Age of Ultron is not just a superhero movie, but a story about parenthood in which the battles take place on the world stage instead of in a living room. Samuel L. Jackson’s Nick Fury is the ultimate father figure, struggling to hold together the superhero team he assembled as they face Ultron (Spader) and a set of evildoing twins: Elizabeth Olsen’s Scarlet Witch and Aaron Taylor-Johnson’s Quicksilver.

These new characters are the products of Baron Wolfgang von Strucker (Thomas Kretschmann), a fresh villain from the dastardly HYDRA organization. He’s been using Loki’s scepter for human experimentation, which bestowed the siblings with powers of magic (Scarlet Witch) and speed (Quicksilver).

But the bad baron piques Tony Stark’s interest for other reasons. “Von Strucker was working on a lot of stuff, including robotics,” says Marvel Studios president Kevin Feige. “Tony realizes, ‘[Those robotics] might be able to help me get over the hump of some of the AI stuff I’ve been working on.’” Stark’s invention, Ultron, is born from the marriage of both men’s technologies. Alas, adolescence is a bitch, and Ultron goes rogue, shreds Stark’s other artificial-intelligence program, J.A.R.V.I.S., and gives rise to his own awesome creation: the synthezoid known as the Vision (played by Paul Bettany, who previously voiced J.A.R.V.I.S.).

Meanwhile, there’s some serious interpersonal drama brewing between the superheroes themselves. For starters, that romance hinted at in the trailer between Scarlett Johansson’s Natasha Romanoff and Mark Ruffalo’s Hulk alter-ego, Bruce Banner, is real. Though this isn’t completely new territory for Marvel movies—see: Tony Stark and Pepper Potts, Thor and Jane Foster, Steve Rogers and Peggy Carter—this is the first time any of the actual Avengers have been tempted to fish off the company pier. Why match up Black Widow with the big green guy? Whedon answers in song, crooning, “‘Tale as old as time…’” from Beauty and the Beast. “It made perfect sense to me,” he says.

If Black Widow has felt like the Avengers’ big sister—cleaning up the messes and keeping the boys in line—that’s precisely why she’s drawn to the Hulk. Whedon says he wanted to pair “the person who’s the most in control with the person who hasto be in control, because he’s the least in control.”

Audiences can also expect a few superpowered cameos, including Falcon (Anthony Mackie), and two top secret new female characters played by Julie Delpy (Before Midnight) and Linda Cardellini (Bloodline). Feige won’t say whom they play, but vowed that Captain Marvel wouldn’t be turning up this time. Sorry, fanboys and fangirls.

Regardless of Age of Ultron’s critical and box office outcome, the next time the Avengers come together—for the two-part Infinity War, planned for 2018 and 2019—Whedon will be nowhere in sight. Joe and Anthony Russo, who directed Captain America: The Winter Soldier and are now in preproduction on next year’s Captain America: Civil War, will be at the helm.

Marvel characters always seem to be creating their own worst enemies, which may explain why Whedon is ready to hang it up: He’s created his own too. “Every movie I have ever made has been an ensemble piece of increasingly enormous proportions,” he says, sitting next to Feige in the editing suite. “That many balls in the air, it’s only going to get bigger with Infinity War. I’m not going to be able to give it what I would need to.” He rasps in a geezer voice: “It’s a young man’s game.”

Maybe. But he still sounds like someone who’s been grandfathered in. Or maybe, uh, Godfathered.

“Just when you think you’re out,” Feige says, doing his best Al Pacino impression, “you get pulled back in.” Whedon points a finger at his soon-to-be-former boss: “That’s the other reason I’m not making a third one.”